Nitrogen application rates influence on yield and water productivity of quinoa under saline irrigation water regimes and saline water table

There are areas with high saline water and saline irrigation water in Iran that may be used for quinoa cultivation. In these conditions, proper saline irrigation water regimes and nitrogen application should be determined and used. Therefore, the aim of this experiment is to investigate the effect of different saline irrigation water regimes (100, 75 and 50% of full irrigation, FI) and nitrogen application rates (0, 100, 200 and 300 kg ha−1) on growth and yield of quinoa with water table depth of 0.8 m, salinity of irrigation water and water table of 20 dS m−1. The irrigation of 75% FI and 50% FI decreased the applied water by 19 and 38%, respectively. Further, there was no reducing effect of irrigation water regimes in seed and shoot dry matter yield. Furthermore, groundwater contribution (GWC) increased significantly by 8 and 18% in 75%FI and 50%FI compared with that obtained in full irrigation, and resulted in no extreme water stress under high water table depth (0.8 m). Increasing application of nitrogen fertilizer significantly increased the yield components, ETc and GWC. In addition, reducing irrigation water did not show a significant decrease in water use efficiency (WUE) in high water table depth. However, water productivity increased significantly by decreasing irrigation water. It is concluded that under deficit irrigation, high water table depth could be a valuable source of water supply to meet quinoa water requirements. Moreover, application of nitrogen fertilizer at all levels significantly increased water use efficiency and water productivity.